fix(m5): add data-testid to payment rows; upgrade E2E spec with proper selectors

app/(app)/payments/page.tsx

@@ -90,7 +90,7 @@ export default function PaymentsPage() {
               ) : payments.length === 0 ? (
                 <EmptyState colSpan={7} message="No payments found" icon={<CreditCard size={24} />} />
               ) : payments.map(p => (
-                <TableRow key={p.id} onClick={() => setSelected(p)} className="cursor-pointer hover:bg-blue-50 transition-colors">
+                <TableRow key={p.id} data-testid="payment-row" onClick={() => setSelected(p)} className="cursor-pointer hover:bg-blue-50 transition-colors">
                   <Td className="text-sm">{p.paymentDate ? formatDate(p.paymentDate) : formatDate(p.createdAt)}</Td>
                   <Td className="font-medium">
                     {p.client ? `${p.client.firstName} ${p.client.lastName}` : "—"}